1. Field of the Invention
The present invention relates to a heat-sensitive recording material. More specifically, the present invention relates to a superior heat-sensitive recording material comprising a support, which is comprised of a substrate and a thermoplastic resin layer formed thereon, and a heat-sensitive recording layer disposed on the support, said heat-sensitive recording material being advantageous in that a fixing process is not inhibited at the time of image recording, the fixing time required is short, and the background region after the fixing process is white.
2. Description of the Related Art
When a heat-sensitive recording material containing a diazonium salt compound is used, the image recording process comprises heating the heat-sensitive recording material by a thermal head or the like, followed by a fixing process wherein the diazonium compound, which was not used for the image formation, is decomposed by irradiation with ultraviolet light. Since the background region after the fixing process is required to be as white as possible, a fluorescent brightening agent is added to the heat-sensitive recording layer. The use of the fluorescent brightening agent, however, presents a problem that the fluorescent brightening agent absorbs the ultraviolet light and inhibits the progress of the fixing process. Therefore the time required for the fixing process is prolonged speed up in the fixing process is impossible. A method has been proposed, wherein a fluorescent brightening agent, which is represented by UBITEX OB and has a bis(alkyl-substituted benzooxazolyl)thiophene-based structure, is added to a thermoplastic resin layer. However, this method is associated with the problem that a thermal treatment in an image recording process causes the bleeding out of the fluorescent brightening agent and therefore the whiteness of the background region is impaired.